Add support for appending task attributes

This commit add support for appending task attributes rather than only
setting them. This is useful for Kotlin's compiler arguments as these
can be augmented by other plugins.

Closes gh-1368

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/code/kotlin/GroovyDslKotlinGradleBuildCustomizer.java

@@ -16,6 +16,7 @@
 
 package io.spring.initializr.generator.spring.code.kotlin;
 
+import java.util.List;
 import java.util.stream.Collectors;
 
 import io.spring.initializr.generator.buildsystem.gradle.GradleTask;
@@ -35,13 +36,17 @@ class GroovyDslKotlinGradleBuildCustomizer extends KotlinGradleBuildCustomizer {
 	@Override
 	protected void customizeKotlinOptions(KotlinProjectSettings settings, GradleTask.Builder compile) {
 		compile.nested("kotlinOptions", (kotlinOptions) -> {
-			String compilerArgs = settings.getCompilerArgs()
-				.stream()
-				.map((arg) -> "'" + arg + "'")
-				.collect(Collectors.joining(", "));
-			kotlinOptions.attribute("freeCompilerArgs", "[" + compilerArgs + "]");
+			kotlinOptions.append("freeCompilerArgs", compilerArgsAsString(settings.getCompilerArgs()));
 			kotlinOptions.attribute("jvmTarget", "'" + settings.getJvmTarget() + "'");
 		});
 	}
 
+	private String compilerArgsAsString(List<String> compilerArgs) {
+		if (compilerArgs.size() == 1) {
+			return "'" + compilerArgs.get(0) + "'";
+		}
+		String values = compilerArgs.stream().map((arg) -> "'" + arg + "'").collect(Collectors.joining(", "));
+		return "[%s]".formatted(values);
+	}
+
 }

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/code/kotlin/KotlinDslKotlinGradleBuildCustomizer.java

@@ -16,6 +16,7 @@
 
 package io.spring.initializr.generator.spring.code.kotlin;
 
+import java.util.List;
 import java.util.stream.Collectors;
 
 import io.spring.initializr.generator.buildsystem.gradle.GradleTask;
@@ -35,13 +36,17 @@ class KotlinDslKotlinGradleBuildCustomizer extends KotlinGradleBuildCustomizer {
 	@Override
 	protected void customizeKotlinOptions(KotlinProjectSettings settings, GradleTask.Builder compile) {
 		compile.nested("kotlinOptions", (kotlinOptions) -> {
-			String compilerArgs = settings.getCompilerArgs()
-				.stream()
-				.map((arg) -> "\"" + arg + "\"")
-				.collect(Collectors.joining(", "));
-			kotlinOptions.attribute("freeCompilerArgs", "listOf(" + compilerArgs + ")");
+			kotlinOptions.append("freeCompilerArgs", compilerArgsAsString(settings.getCompilerArgs()));
 			kotlinOptions.attribute("jvmTarget", "\"" + settings.getJvmTarget() + "\"");
 		});
 	}
 
+	private String compilerArgsAsString(List<String> compilerArgs) {
+		if (compilerArgs.size() == 1) {
+			return "\"" + compilerArgs.get(0) + "\"";
+		}
+		String values = compilerArgs.stream().map((arg) -> "\"" + arg + "\"").collect(Collectors.joining(", "));
+		return "listOf(%s)".formatted(values);
+	}
+
 }

initializr-generator-spring/src/test/java/io/spring/initializr/generator/spring/code/kotlin/GroovyDslKotlinGradleBuildCustomizerTests.java

@@ -16,8 +16,11 @@
 
 package io.spring.initializr.generator.spring.code.kotlin;
 
+import java.util.List;
+
 import io.spring.initializr.generator.buildsystem.gradle.GradleBuild;
 import io.spring.initializr.generator.buildsystem.gradle.GradleTask;
+import io.spring.initializr.generator.buildsystem.gradle.GradleTask.Attribute;
 import org.assertj.core.groups.Tuple;
 import org.junit.jupiter.api.Test;
 
@@ -51,6 +54,23 @@ class GroovyDslKotlinGradleBuildCustomizerTests {
 		});
 	}
 
+	@Test
+	void kotlinCompilationTasksWithListOfCompilerArgsAreCustomizer() {
+		GradleBuild build = new GradleBuild();
+		KotlinProjectSettings kotlinProjectSettings = new SimpleKotlinProjectSettings("1.2.70", "11") {
+			@Override
+			public List<String> getCompilerArgs() {
+				return List.of("-Xjsr305=strict", "-Xmx=128M");
+			}
+		};
+		new GroovyDslKotlinGradleBuildCustomizer(kotlinProjectSettings).customize(build);
+		assertThat(build.tasks().values()).singleElement().satisfies((task) -> {
+			GradleTask kotlinOptions = task.getNested().get("kotlinOptions");
+			assertThat(kotlinOptions.getAttributes())
+				.contains(Attribute.append("freeCompilerArgs", "['-Xjsr305=strict', '-Xmx=128M']"));
+		});
+	}
+
 	private void assertKotlinOptions(GradleTask compileTask, String jvmTarget) {
 		assertThat(compileTask.getAttributes()).isEmpty();
 		assertThat(compileTask.getInvocations()).isEmpty();
@@ -59,8 +79,8 @@ class GroovyDslKotlinGradleBuildCustomizerTests {
 		assertThat(kotlinOptions.getInvocations()).hasSize(0);
 		assertThat(kotlinOptions.getNested()).hasSize(0);
 		assertThat(kotlinOptions.getAttributes()).hasSize(2);
-		assertThat(kotlinOptions.getAttributes()).containsEntry("freeCompilerArgs", "['-Xjsr305=strict']")
-			.containsEntry("jvmTarget", String.format("'%s'", jvmTarget));
+		assertThat(kotlinOptions.getAttributes()).contains(Attribute.append("freeCompilerArgs", "'-Xjsr305=strict'"),
+				Attribute.set("jvmTarget", String.format("'%s'", jvmTarget)));
 	}
 
 }

initializr-generator-spring/src/test/java/io/spring/initializr/generator/spring/code/kotlin/KotlinDslKotlinGradleBuildCustomizerTests.java

@@ -16,8 +16,11 @@
 
 package io.spring.initializr.generator.spring.code.kotlin;
 
+import java.util.List;
+
 import io.spring.initializr.generator.buildsystem.gradle.GradleBuild;
 import io.spring.initializr.generator.buildsystem.gradle.GradleTask;
+import io.spring.initializr.generator.buildsystem.gradle.GradleTask.Attribute;
 import org.assertj.core.groups.Tuple;
 import org.junit.jupiter.api.Test;
 
@@ -50,6 +53,23 @@ class KotlinDslKotlinGradleBuildCustomizerTests {
 		});
 	}
 
+	@Test
+	void kotlinCompilationTasksWithListOfCompilerArgsAreCustomized() {
+		GradleBuild build = new GradleBuild();
+		KotlinProjectSettings kotlinProjectSettings = new SimpleKotlinProjectSettings("1.2.70", "11") {
+			@Override
+			public List<String> getCompilerArgs() {
+				return List.of("-Xjsr305=strict", "-Xmx=128M");
+			}
+		};
+		new KotlinDslKotlinGradleBuildCustomizer(kotlinProjectSettings).customize(build);
+		assertThat(build.tasks().values()).singleElement().satisfies((task) -> {
+			GradleTask kotlinOptions = task.getNested().get("kotlinOptions");
+			assertThat(kotlinOptions.getAttributes())
+				.contains(Attribute.append("freeCompilerArgs", "listOf(\"-Xjsr305=strict\", \"-Xmx=128M\")"));
+		});
+	}
+
 	private void assertKotlinOptions(GradleTask compileTask, String jvmTarget) {
 		assertThat(compileTask.getAttributes()).isEmpty();
 		assertThat(compileTask.getInvocations()).isEmpty();
@@ -58,8 +78,8 @@ class KotlinDslKotlinGradleBuildCustomizerTests {
 		assertThat(kotlinOptions.getInvocations()).hasSize(0);
 		assertThat(kotlinOptions.getNested()).hasSize(0);
 		assertThat(kotlinOptions.getAttributes()).hasSize(2);
-		assertThat(kotlinOptions.getAttributes()).containsEntry("freeCompilerArgs", "listOf(\"-Xjsr305=strict\")")
-			.containsEntry("jvmTarget", String.format("\"%s\"", jvmTarget));
+		assertThat(kotlinOptions.getAttributes()).contains(Attribute.append("freeCompilerArgs", "\"-Xjsr305=strict\""),
+				Attribute.set("jvmTarget", String.format("\"%s\"", jvmTarget)));
 	}
 
 }

initializr-generator-spring/src/test/resources/project/gradle/kotlin-java11-build.gradle.gen

@@ -26,7 +26,7 @@ dependencies {
 
 tasks.withType(KotlinCompile) {
 	kotlinOptions {
-		freeCompilerArgs = ['-Xjsr305=strict']
+		freeCompilerArgs += '-Xjsr305=strict'
 		jvmTarget = '11'
 	}
 }

initializr-generator-spring/src/test/resources/project/gradle/kotlin-java11-build.gradle.kts.gen

@@ -26,7 +26,7 @@ dependencies {
 
 tasks.withType<KotlinCompile> {
 	kotlinOptions {
-		freeCompilerArgs = listOf("-Xjsr305=strict")
+		freeCompilerArgs += "-Xjsr305=strict"
 		jvmTarget = "11"
 	}
 }

initializr-generator-spring/src/test/resources/project/kotlin/standard/build.gradle.gen

@@ -26,7 +26,7 @@ dependencies {
 
 tasks.withType(KotlinCompile) {
 	kotlinOptions {
-		freeCompilerArgs = ['-Xjsr305=strict']
+		freeCompilerArgs += '-Xjsr305=strict'
 		jvmTarget = '1.8'
 	}
 }

initializr-generator-spring/src/test/resources/project/kotlin/standard/build.gradle.kts.gen

@@ -26,7 +26,7 @@ dependencies {
 
 tasks.withType<KotlinCompile> {
 	kotlinOptions {
-		freeCompilerArgs = listOf("-Xjsr305=strict")
+		freeCompilerArgs += "-Xjsr305=strict"
 		jvmTarget = "1.8"
 	}
 }

initializr-generator-spring/src/test/resources/project/kotlin/standard/war-build.gradle.gen

@@ -28,7 +28,7 @@ dependencies {
 
 tasks.withType(KotlinCompile) {
 	kotlinOptions {
-		freeCompilerArgs = ['-Xjsr305=strict']
+		freeCompilerArgs += '-Xjsr305=strict'
 		jvmTarget = '1.8'
 	}
 }

initializr-generator-spring/src/test/resources/project/kotlin/standard/war-build.gradle.kts.gen

@@ -28,7 +28,7 @@ dependencies {
 
 tasks.withType<KotlinCompile> {
 	kotlinOptions {
-		freeCompilerArgs = listOf("-Xjsr305=strict")
+		freeCompilerArgs += "-Xjsr305=strict"
 		jvmTarget = "1.8"
 	}
 }

initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/GradleBuildWriter.java

@@ -38,6 +38,7 @@ import io.spring.initializr.generator.buildsystem.DependencyContainer;
 import io.spring.initializr.generator.buildsystem.DependencyScope;
 import io.spring.initializr.generator.buildsystem.MavenRepository;
 import io.spring.initializr.generator.buildsystem.PropertyContainer;
+import io.spring.initializr.generator.buildsystem.gradle.GradleTask.Attribute.Type;
 import io.spring.initializr.generator.io.IndentingWriter;
 import io.spring.initializr.generator.version.VersionProperty;
 
@@ -200,7 +201,7 @@ public abstract class GradleBuildWriter {
 
 	protected final void writeTaskCustomization(IndentingWriter writer, GradleTask task) {
 		writeCollection(writer, task.getInvocations(), this::invocationAsString);
-		writeMap(writer, task.getAttributes(), (key, value) -> key + " = " + value);
+		writeCollection(writer, task.getAttributes(), this::attributeAsString);
 		task.getNested().forEach((property, nestedCustomization) -> {
 			writer.println(property + " {");
 			writer.indented(() -> writeTaskCustomization(writer, nestedCustomization));
@@ -208,6 +209,11 @@ public abstract class GradleBuildWriter {
 		});
 	}
 
+	private String attributeAsString(GradleTask.Attribute attribute) {
+		String separator = (attribute.getType() == Type.SET) ? "=" : "+=";
+		return String.format("%s %s %s", attribute.getName(), separator, attribute.getValue());
+	}
+
 	protected abstract String invocationAsString(GradleTask.Invocation invocation);
 
 	private void writeSnippets(IndentingWriter writer, GradleSnippetContainer snippets) {

initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/GradleTask.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -22,6 +22,7 @@ import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.function.Consumer;
 
 /**
@@ -35,7 +36,7 @@ public class GradleTask {
 
 	private final String type;
 
-	private final Map<String, String> attributes;
+	private final List<Attribute> attributes;
 
 	private final List<Invocation> invocations;
 
@@ -44,7 +45,7 @@ public class GradleTask {
 	protected GradleTask(Builder builder) {
 		this.name = builder.name;
 		this.type = builder.type;
-		this.attributes = Collections.unmodifiableMap(new LinkedHashMap<>(builder.attributes));
+		this.attributes = List.copyOf(builder.attributes.values());
 		this.invocations = Collections.unmodifiableList(new ArrayList<>(builder.invocations));
 		this.nested = Collections.unmodifiableMap(resolve(builder.nested));
 	}
@@ -73,10 +74,10 @@ public class GradleTask {
 	}
 
 	/**
-	 * Return the attributes that should be set for this task.
+	 * Return the attributes that should be configured for this task.
 	 * @return task attributes
 	 */
-	public Map<String, String> getAttributes() {
+	public List<Attribute> getAttributes() {
 		return this.attributes;
 	}
 
@@ -105,7 +106,7 @@ public class GradleTask {
 
 		private final String type;
 
-		private final Map<String, String> attributes = new LinkedHashMap<>();
+		private final Map<String, Attribute> attributes = new LinkedHashMap<>();
 
 		private final List<Invocation> invocations = new ArrayList<>();
 
@@ -121,12 +122,21 @@ public class GradleTask {
 		}
 
 		/**
-		 * Add a task attribute.
+		 * Set a task attribute.
 		 * @param target the name of the attribute
 		 * @param value the value
 		 */
 		public void attribute(String target, String value) {
-			this.attributes.put(target, value);
+			this.attributes.put(target, Attribute.set(target, value));
+		}
+
+		/**
+		 * Configure a task attribute by appending the specified value.
+		 * @param target the name of the attribute
+		 * @param value the value to append
+		 */
+		public void append(String target, String value) {
+			this.attributes.put(target, Attribute.append(target, value));
 		}
 
 		/**
@@ -191,4 +201,104 @@ public class GradleTask {
 
 	}
 
+	/**
+	 * An attribute of a task.
+	 */
+	public static final class Attribute {
+
+		private final String name;
+
+		private final String value;
+
+		private final Type type;
+
+		private Attribute(String name, String value, Type type) {
+			this.name = name;
+			this.value = value;
+			this.type = type;
+		}
+
+		/**
+		 * Create an attribute that {@linkplain Type#SET sets} the specified value.
+		 * @param name the name of the attribute
+		 * @param value the value to set
+		 * @return an attribute
+		 */
+		public static Attribute set(String name, String value) {
+			return new Attribute(name, value, Type.SET);
+		}
+
+		/**
+		 * Create an attribute that {@linkplain Type#APPEND appends} the specified value.
+		 * @param name the name of the attribute
+		 * @param value the value to append
+		 * @return an attribute
+		 */
+		public static Attribute append(String name, String value) {
+			return new Attribute(name, value, Type.APPEND);
+		}
+
+		/**
+		 * Return the name of the attribute.
+		 * @return the name
+		 */
+		public String getName() {
+			return this.name;
+		}
+
+		/**
+		 * Return the value of the attribute to set or to append.
+		 * @return the value
+		 */
+		public String getValue() {
+			return this.value;
+		}
+
+		/**
+		 * Return the {@link Type} of the attribute.
+		 * @return the type
+		 */
+		public Type getType() {
+			return this.type;
+		}
+
+		@Override
+		public boolean equals(Object o) {
+			if (this == o) {
+				return true;
+			}
+			if (o == null || getClass() != o.getClass()) {
+				return false;
+			}
+			Attribute attribute = (Attribute) o;
+			return Objects.equals(this.name, attribute.name) && Objects.equals(this.value, attribute.value)
+					&& this.type == attribute.type;
+		}
+
+		@Override
+		public int hashCode() {
+			return Objects.hash(this.name, this.value, this.type);
+		}
+
+		@Override
+		public String toString() {
+			return this.name + ((this.type == Type.SET) ? " = " : " += ") + this.value;
+		}
+
+		public enum Type {
+
+			/**
+			 * Set the value of the attribute.
+			 */
+			SET,
+
+			/**
+			 * Append the value to the attribute.
+			 */
+			APPEND;
+
+		}
+
+	}
+
 }

initializr-generator/src/test/java/io/spring/initializr/generator/buildsystem/gradle/GradleTaskContainerTests.java

@@ -16,10 +16,10 @@
 
 package io.spring.initializr.generator.buildsystem.gradle;
 
+import io.spring.initializr.generator.buildsystem.gradle.GradleTask.Attribute;
 import org.junit.jupiter.api.Test;
 
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.entry;
 
 /**
  * Tests for {@link GradleTaskContainer}.
@@ -73,11 +73,15 @@ class GradleTaskContainerTests {
 	@Test
 	void customizeTask() {
 		GradleTaskContainer container = new GradleTaskContainer();
-		container.customize("test", (task) -> task.attribute("fork", "true"));
+		container.customize("test", (task) -> {
+			task.attribute("fork", "true");
+			task.append("names", "test");
+		});
 		assertThat(container.values()).singleElement().satisfies((task) -> {
 			assertThat(task.getName()).isEqualTo("test");
 			assertThat(task.getType()).isNull();
-			assertThat(task.getAttributes()).containsOnly(entry("fork", "true"));
+			assertThat(task.getAttributes()).containsOnly(Attribute.set("fork", "true"),
+					Attribute.append("names", "test"));
 			assertThat(task.getInvocations()).isEmpty();
 			assertThat(task.getNested()).isEmpty();
 		});
@@ -93,7 +97,7 @@ class GradleTaskContainerTests {
 		assertThat(container.values()).singleElement().satisfies((task) -> {
 			assertThat(task.getName()).isEqualTo("MyTask");
 			assertThat(task.getType()).isEqualTo("com.example.MyTask");
-			assertThat(task.getAttributes()).containsOnly(entry("fork", "true"));
+			assertThat(task.getAttributes()).containsOnly(Attribute.set("fork", "true"));
 			assertThat(task.getInvocations()).singleElement().satisfies((invocation) -> {
 				assertThat(invocation.getTarget()).isEqualTo("property");
 				assertThat(invocation.getArguments()).containsOnly("taskDir");
@@ -116,7 +120,8 @@ class GradleTaskContainerTests {
 		assertThat(container.values()).singleElement().satisfies((task) -> {
 			assertThat(task.getName()).isEqualTo("test");
 			assertThat(task.getType()).isNull();
-			assertThat(task.getAttributes()).containsOnly(entry("ignore", "false"), entry("fork", "false"));
+			assertThat(task.getAttributes()).containsOnly(Attribute.set("ignore", "false"),
+					Attribute.set("fork", "false"));
 			assertThat(task.getInvocations()).singleElement().satisfies((invocation) -> {
 				assertThat(invocation.getTarget()).isEqualTo("method");
 				assertThat(invocation.getArguments()).containsOnly("arg1", "arg2");

initializr-generator/src/test/java/io/spring/initializr/generator/buildsystem/gradle/GradleTaskTests.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2012-2023 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.spring.initializr.generator.buildsystem.gradle;
+
+import io.spring.initializr.generator.buildsystem.gradle.GradleTask.Attribute;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link GradleTask}.
+ *
+ * @author Stephane Nicoll
+ */
+public class GradleTaskTests {
+
+	@Test
+	void attributeSetHasSensibleToString() {
+		assertThat(Attribute.set("name", "value")).hasToString("name = value");
+	}
+
+	@Test
+	void attributeAppendHasSensibleToString() {
+		assertThat(Attribute.append("name", "value")).hasToString("name += value");
+	}
+
+}